First, he was alleged to have been a historian, but most of his writings are lost. Why has nobody attempted to track down a few? surely somebody bought a copy somewhere. I know papyrus does not do well with age, but is there even a tiny possibilty that something might be hiding in North Africa, Turkey, or (slim chance) that library in Herculaneum?)

That's not how discovery of ancient texts works. It's totally unreasonable to go actually looking for a particular text. Settlement during antiquity covered an enormous area, the number of sites that would have to be investigated is simply impossible. Add to that the fact that most sites aren't fully excavated and the fact that there are thousands of sites that we don't even know about and you can see why it would be an impossible enterprise--besides the difficulties with even finding a text at all it's just impossible to find a particular one. The written output of antiquity was vast, and we only have a tiny fraction of everything that was written. This leads us to the second fact of papyrology that I think you're missing--with only a handful of exceptions our complete texts are not papyri and never will be. Our manuscripts are almost all medieval copies of ancient texts. These are preserved more readily, and since multiple copies of these texts would be copied and recopied throughout the Middle Ages we usually have several different copies. That causes problems for other reasons, but frankly the amount of complete works that we have only from papyri is insignificant--the only complete text I can think of off the top of my head preserved only in papyrus is Menander's Dyskolos. Papyrus rarely yields anything but fragments, and a work like Claudius' histories, which were in multiple books, is not going to be preserved in its entirety, or even in any length, from papyrus alone. Our lack of ancient texts is due partly to the fact that papyrus really doesn't get preserved very well (apart from places like Oxyrhynchus, which is a perfect example of what I'm talking about--Oxyrhynchus was essentially a trash dump, with conditions perfect for preserving papyri, yet just about everything from Oxyrhynchus is fragmentary) but also due to the fact that later copyists selectively chose what was to be copied. This is not just a medieval phenomenon, ancient scribes picked and chose as well--several authors and works are known to have been largely lost by late antiquity already, since nobody bothered to copy them. Books were copied by hand, and editions wouldn't survive all that long in the scheme of things. Antiquity is long and paper doesn't last all that long--authors like Catullus, who fell out of style sometime during the Principate, were almost completely lost by late antiquity because nobody was still copying those books (Catullus was only rediscovered in a single manuscript, now lost, in the Middle Ages, having thought to have been totally lost). Besides that church copyists had to prioritize sometimes their limited resources. There's a good deal of evidence to suggest that what we've got is fairly representative of the "greatest hits," so to speak, of the ancient literary tradition, but it's still incomplete. There are literally thousands of texts out there that we know about and would like to have, and Claudius' histories are only a few of many. It's possible that a medieval manuscript might show up, but it's extremely unlikely, and papyrus finds simply aren't going to give us more than fragments, even if they exist (and for what it's worth, the Villa of Papyri at Herculaneum almost certainly doesn't contain Claudius' histories, it was probably Piso's private collection of Philodemus' and other Epicureans' writings).

Second, why is he not better remembered? Augustus is the rock star of that dynasty, the name no child forgets, but Claudius does not get much credit ( remember that Caligula nearly bankrupted Rome; Claudius made reforms and Romans at least got to eat.) have any historians ever attempted to find out more about him recently?

I'd say that Claudius is most definitely well-remembered. The success of I, Claudius ensured this. In my experience if anyone knows a second Roman emperor after Augustus it's either Caligula or Claudius, due to the film Caligula and I, Claudius--the mother of a friend of mine when I was a kid, who was shocked to learn that Cleopatra was a Macedonian and not a native Egyptian, knew a fair amount about Claudius through I, Claudius. In any case, Claudius' reign is very contested among scholars. The balance is that Claudius' reign was relatively stable, especially compared to those of his successors, but we shouldn't go too far. Claudius' reputation suffered heavily under Nero, who pointed out his many failings, and although he was the only Julio-Claudian besides Augustus to be deified he had a very mixed reputation even later--Vespasian and the Flavians held him up as a model, in contrast to their condemnation of Nero, but Tacitus was mercilessly scathing in his opinion of Claudius. Claudius was by no means a bad emperor, but it's easy to swing too far in reaction against the condemnation of our ancient texts--as the OCD says, "Modern writers have overreacted, exaggerating his purposefulness in encouraging the development of the provinces; his accession and survival, preserving the imperial peace, and his recognition of social changes were his main domestic achievements." Claudius did a lot of impressive things, especially his expansion of citizenship and his building projects, but his reign was fraught with over-reliance on his freedmen, who were notoriously corrupt, his misplaced trust in people like Messallina, and a flagrant disregard for the regular rules of of government that he was ostensibly trying to defend (in particular his private trials and his repeated bypassing of the senate's opinion). Even his influence in building up the provinces can be taken too far--Claudius was important in that regard, but it's been pretty convincingly suggested that Nero, particularly in the east, was incredibly influential in the development of the provinces, so much so that some have painted Nero as an emperor of the provinces rather than one of the city. Also, with regards to Caligula's expenditure it's usually thought that it was ultimately beneficial for Rome, although perhaps by accident. Caligula's private, pleasure-intended projects like his bridge across the Bay of Naples are usually emphasized, but Caligula was quite keen on the expansion of the network of roads and began the building of the Aqua Claudia--his expansions to the harbor at Rhegium were specifically intended to improve the grain supply to Italy, and were apparently successful. Tiberius' reign had left the economy of the empire, and particularly Italy, in a languid period of stagnation--whether intentional or not, Caligula's expenditures very much helped kick off the state's economy again and Claudius' building projects should be very much thought of as a continuation of Caligula's

What is the current consensus on Claudius's disability? I have read a lot about Cerebral palsy, but what about MS? Has anybody considered it mught be more than one disability?

There have been quite a lot of suggestions, but retrospective diagnosis is a notoriously unreliable practice, one that I've written about before on this sub. Retrospective diagnosis is also not something that historians and classicists bother with very much, because it's really not that useful or important--it's an interesting question to know what Claudius' disease was (Claudius has been suggested as being afflicted by anything from cerebral palsy to autism) but it doesn't really get us anywhere and in the end it doesn't especially matter much.